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A385715 Square array read by descending antidiagonals: A(n,k) is the number of fixed n-dimensional (n,2)-polyominoids, n >= 2, of size k >= 1.

%I A385715 #16 Jul 13 2025 12:51:11
%S A385715 1,2,3,6,18,6,19,158,60,10,63,1611,916,140,15,216,17811,16698,3060,
%T A385715 270,21,760,207395,336210,81090,7690,462,28,2725,2505858,7218768,
%U A385715 2396434,268005,16226,728,36,9910,31125711,162185112,76020890,10477161,701589,30408,1080,45
%N A385715 Square array read by descending antidiagonals: A(n,k) is the number of fixed n-dimensional (n,2)-polyominoids, n >= 2, of size k >= 1.
%H A385715 Wikipedia, <a href="https://en.wikipedia.org/wiki/Polyominoid">Polyominoid</a>.
%H A385715 <a href="/index/Pol#polyominoes">Index entries for sequences related to polyominoes</a>.
%e A385715 The top corner of the array (size on horizontal axis, dimensions on vertical):
%e A385715               1    2     3       4         5          6           7           8         9         10
%e A385715 (A001168) 2:  1    2     6      19        63        216         760        2725      9910      36446
%e A385715 (A075678) 3:  3   18   158    1611     17811     207395     2505858    31125711 394982973 5098498323
%e A385715 (A366335) 4:  6   60   916   16698    336210    7218768   162185112  3769221330
%e A385715           5: 10  140  3060   81090   2396434   76020890  2535403620 87781527395
%e A385715           6: 15  270  7690  268005  10477161  441378400 19603138320
%e A385715           7: 21  462 16226  701589  34160301 1796996509
%e A385715           8: 28  728 30408 1570436  91583156
%e A385715           9: 36 1080 52296 3141108 213477012
%Y A385715 Rows: A001168 (n=2), A075678 (n=3), A366335 (n=4).
%Y A385715 Columns: A000217 (k=1), A213820 (k=2).
%Y A385715 Cf. A385291 (polyominoes), A385581 (polysticks).
%K A385715 nonn,tabl
%O A385715 2,2
%A A385715 _John Mason_, Jul 07 2025